Every 45 years, roughly half of the medical knowledge about cirrhosis and hepatitis is disproven or becomes out of date.

“This is about twice the half-life of the actual radioisotope samarium-151,” writes Samuel Arbesman in his book, “The Half-Life of Facts.”

Arbesman’s book argues that we can measure the obsolescence of knowledge and facts the same way we measure radioactive decay. “It turns out knowledge is a lot like radioactive atoms because it decays over time,” he wrote in a Harvard Business Review article adapted from the book. “And when we’re dealing with large amount of facts and information, we can actually predict how long it will take for it to spread or decay by applying the laws of mathematics.”

We don’t have the same calculations for news articles, but the recent launch of Vox.com provided an interesting bit of data.

The half-life of cardstacks

In their launch post, the site’s cofounders described Vox as an effort to “build the vast repository of information that will make it possible for us to explain the news in real time.”

They want to provide a comprehensive place to read the latest news while also enabling people to understand the context thanks to explainers (formatted as card stacks) offering the necessary background. It’s real-time news plus rapidly updated topic pages.

It’s also a huge challenge, due to the rapid decay of facts related to news stories and current events.

To attain its goal, Vox has to create and maintain in close to real time stacks of cards about an ever-evolving and increasing set of topics related to public policy, politics, world events, and myriad other areas. Adding to the challenge is the reality that facts about these topics will change at any given moment due to a news event, or something more obscure, such as a government report or academic research paper.

For example, soon after Vox’s launch, a card about the crisis in Ukraine needed to be updated to reflect new facts. Since then, another card in that stack was updated “to reflect a UN draft report on election abuses in Crimea’s referendum vote.” In all, there have been five Ukraine cards updated and one added in about two weeks. A card stack about income inequality has been updated three times. (Not all those updates were a result of new facts coming to light, but they nevertheless required someone to make changes.)

The gender wage gap card stack hasn’t yet had any changes, but its final card is entitled “What else should I be reading about the wage gap?” That reading list will need to stay current in order to offer value. (There’s also a joke to be made about the number of updates that a card stack about Congressional dysfunction will warrant — but I’ll just note that so far it’s been updated once.)

As a point of comparison, I asked David Cohn, chief content officer of mobile news app Circa, how many times they’ve made new updates to their ever-evolving story about the missing Malaysian Airlines plane. Cohn said they’ve officially made more than 20 updates since the flight went missing on March 8. He added that the number of changes to the story would be even higher if you counted each tweak and addition.

The faster a card stack is overcome by new facts, the more frequently the Vox team will need to make updates. The more card stacks they create, the more complicated it will be to keep all of them current.

“We want them very basic,” Klein told New York magazine when asked about the kind of topics they will tackle in card stacks. That means a lot of card stacks — and a lot of facts and knowledge to manage. As of this writing, there are 17 card stacks displayed on the Vox’s “cards” page, though that’s not the full count of what they’ve produced. Vox could easily get to 50 card stacks by the end of the month. And on and on and on…

This is what it means to aspire to a “vast repository of information.” It makes the 45-year half-life for cirrhosis research seem downright glacial. It’s not hard to imagine a card stack having a half-life of 45 hours due to new developments. Others may be current for weeks or even months. Then, suddenly, they’ll need to be updated. Someone at Vox is going to need to know which card stacks to update when, and to deploy the right person(s) it quickly. Otherwise, they’ll have out-of-date explainers. No one wants a vast repository of old information.

A managing editor for facts?

“[I]n the 1970s librarians everywhere were coping with the very real implications of the exponential growth of knowledge: Their libraries were being inundated,” writes Arbesman in his book. He continues:

They needed ways to figure out which volumes they could safely discard. If they knew the half-life of a book or article’s time of obsolescence, it would go a long way to providing a means to avoid overloading a library’s capacity. Knowing the half-lives of a library’s volumes would give a librarian a handle on how long books should be kept before they are just taking up space on the shelves, without being useful.

In the context of Vox, it’s less about space constraints and knowing what to discard; it’s about the challenge of unlimited topics and the rapid obsolescence of facts related to those topics.

This presents an intriguing challenge: How can Vox keep all of its card stacks as up to date as possible with the least amount of time and effort? What triggers will they use to know which ones to update? Can they begin to predict the update patterns of card stacks in specific topic areas, much like the researchers did with cirrhosis?

I asked Vox cofounder Melissa Bell about the challenge of keeping an ever-growing number of card stacks factually up to date. But this very challenge is one of the things keeping her too busy to talk right now.

“Thank you so much for your interest in my site, and that’s a great question, but the truth is: I am drowning right now,” she wrote back. “I just don’t have a spare second right now. (I need to get to work on making sure we’re meeting that challenge!)”

So, allow me to offer a couple of suggestions without the benefit of insider knowledge. (Which means my facts may soon be obsolete!)

One option for Vox over time is to recruit and reward a Wikipedia-like retinue of volunteer editors who can demonstrate the relevant knowledge to own specific card stacks. To hear Klein talk, Wikipedia is in his sights. “I think it’s weird that the news cedes so much ground to Wikipedia,” he said in the interview with New York magazine.

It’s not hard to understand why news currently cedes the explainer market to Wikipedia. Explaining requires scale and speed to keep pace with the half-life of facts.

The celebrated product folks at Vox Media have an opportunity (or perhaps an imperative) to create a system that helps deploy the right human resources to the right card stacks when needed, and to enable people to ignore the ones that can be left alone. Otherwise, it will be incredibly difficult to scale their explanatory efforts.

Maybe that means a scheduling function for card stacks whereby the owner(s) is reminded that they haven’t updated in x days or weeks. Maybe it means notifications tied to Google Alerts or other sources as a way to nudge a certain card stack to the top of the pile, based on fact-based activity.

One thing I hope happens is that they collect data about card changes — in order to get a sense of the half-life of card stacks and the facts therein. This would guide their efforts, but my admittedly selfish desire is to have better data about the half-life of facts related to newsworthy topics. How will marijuana legalization compare to income inequality? What about the Pope versus bitcoin? Global warming versus fracking?

A final suggestion with no self-interest is that co-founders Melissa Bell, Ezra Klein, and Matthew Yglesias go looking for a research librarian/editor to become their managing editor for facts. After all, who better than a librarian to manage an ever-growing card catalogue?